1. Field of the Invention
The present invention generally pertains to wireless data transmission systems. In particular, the present invention pertains to data transmission in wireless data transmission systems.
2. Discussion of the Related Art
Data telecommunication comprises the reciprocal sending and receiving of data or data signals (packet data) between a data terminal, for example a personal computer, data terminal, data processing system etc., and a remote data terminal, for example a personal computer, data terminal, data processing system etc., over a telecommunication network, for example a public telecommunication network (such as ISDN, PSTN, etc.). To enable the data or data signals sent by the data terminal to be transmitted over the tele-communication network, a technical network device, the so-called data transmission device, is arranged between the data terminal and the tele-communication network. Besides the PC card, formerly known as PCMCIA card, the most commonly used data transmission device is the modem, which is a contraction of modulator/demodulator.
The modem is an electrical data transmission device that operates on the basis of carrier current for use on analog transmission paths having a limited bandwidth, e.g. telecommunication lines, such as a/b line pair, ISDN S0 bus etc., of the telecommunication network, which converts digital data signals into analog data signals and vice versa and transmits them. A large number of V-series Methods standardized by the International Telecommu-nication Unionxe2x80x94Telecommunication Standards (ITU-T) are also implemented in modems.
According to the ITU-T V.24 specification of March 1993, pages 1 to 19, a V.24 cable or a V.24 interface KV.24 supports modem operation on a personal computer over various lines known as status lines. These lines are namely: 1. a transmit data line TxD for data transmission; 2. a receive data line RxD for data transmission; 3. an RTS line (Ready To Send) RTS for the xe2x80x9chardware handshakexe2x80x9d transmission mode for transmitting the status xe2x80x9cREADY TO SENDxe2x80x9d (status xe2x80x9cRTSxe2x80x9d); 4. a CTS line (Clear To Send) CTS for the xe2x80x9chardware handshakexe2x80x9d transmission mode for transmitting the status xe2x80x9cCLEAR TO SENDxe2x80x9d (status xe2x80x9cCTSxe2x80x9d); 5. an RI line (Ring Indication) RI for call detection at the modem; 6. a DSR line (DATA SET READY) DSR on which the modem signals the personal computer that it is switched on; 7. a DTR line (DATA TERMINAL READY) DTR on which the personal computer signals the modem that it is switched on and ready to establish connections; 8. a DCD line (DATA CHANNEL DETECTION) DCD on which the modem signals the personal computer that it has established the connection to a remote modem; and 9. a ground line (GrouND) GND.
If the V.24 cable or the V.24 interface KV.24 does not have the nine lines enumerated above, but has fewer than nine, for example seven, then this 7-conductor cable can nevertheless support modem operation on the personal computer. This is performed by using, instead of xe2x80x9chardware handshakingxe2x80x9d on the RTS/CTS lines, a xe2x80x9csoftware handshakexe2x80x9d transmission mode for transmitting the statuses xe2x80x9cRTSxe2x80x9d, xe2x80x9cCTSxe2x80x9dxe2x80x94for example using an XON/XOFF protocolxe2x80x94on the transmit/receive data lines TxD, RxD. With xe2x80x9csoftware handshakingxe2x80x9d the data stream transmitted between the data terminal DEE and the data transmission device D{haeck over (s)}E is analyzed in the data terminal DEE and the data transmission device D{haeck over (s)}E, all xe2x80x9csoftware handshake charactersxe2x80x9d are interpreted, and actions are initiated accordingly.
Air interfaces are wireless telecommunication interfaces in which messages are wirelessly transmitted over a long-distance transmission path between a message source and a message sink on the basis of various communication methods FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and/or CDMA (Code Division Multiple Access), are set forth according to radio standards such as DECT [Digital Enhanced (formerly: European) Cordless Telecommunication; cf. Nachrichten technik Elektronik 42 (1992) Jan./Feb. No.1, Berlin, DE; U. Pilger xe2x80x9cStruktur des DECT-Standardsxe2x80x9d (Structure of the DECT standard), pages 23 to 29 in conjunction with the ETSI publication ETS 300175-1.9, October 1992 and the DECT publication of the DECT-Forum, February 1997, pages 1 to 16], GSM [Groupe Sp,ciale Mobile or Global System for Mobile Communication; cf. Informatik Spektrum 14 (1991) June, No. 3, Berlin, DE; A. Mann: xe2x80x9cDer GSMS-Standardxe2x80x94Grundlage for digitale Europische Mobilfunknetzexe2x80x9d (The GSM Standardxe2x80x94Basis for Digital European Mobile Radio Networks), pages 137 to 152 in conjunction with the publication telekom praxis 4/1993, P. Smolka xe2x80x9cGSM-Funkschnittstellexe2x80x94Elemente und Funk tionenxe2x80x9d (GSM radio interfacexe2x80x94elements and functions), pages 17 to 24], UMTS [cf. Funkschau 6/98: R. Sietmann xe2x80x9cRingen urn die UMTS-Schnittstellexe2x80x9d (Battle for the UMTS interface), pages 76 to 81], WACS or PACS, IS-54, IS-95, PHS, PDC etc. See also, IEEE Communications Magazine, January 1995, pages 50 to 57; D. D. Falconer et al: xe2x80x9cTime Division Multiple Access Methods for Wireless Personal Communicationsxe2x80x9d.
According to the publication xe2x80x9cVortrag von A. Elberse, M. Barry, G. Fleming zum Thema: xe2x80x9cDECT Data Servicesxe2x80x94DECT in Fixed and Mobile Networksxe2x80x9d, 17/18 June 1996, Sofitel Hotel, Paris; pages 1 to 12 and abstractxe2x80x9d DECT Technology, based on the journal xe2x80x9cNachrichtentechnik Elektronik 42 (1992) Jan./Feb. No. 1, Berlin, DE. See also, U. Pilger xe2x80x9cStruktur des DECT-Standardsxe2x80x9d (Structure of the DECT Standard), pages 23 to 29 in conjunction with the ETSI publication ETS 300175-1.9, October 1992 and the Journals Components 31 (1993), Issue 6, pages 215 to 218; S. Althammer. D. Brockmann: xe2x80x9cHochoptimierte IC""s for DECT-Schnurlostele-fonexe2x80x9d (Super-optimized Ics for DECT cordless telephones), and WO 96/38991. The principal application of DECT (Digital Enhanced Cordless Telecommunication) technology will be in the area of wireless mobile telecommunication of voice and/or packet data, in which, as a result of the DECT network access technology, the user can be both his own network operator and can access a higher telecommunication network for long-distance transmission of user data.
It is an object of the present invention to provie a method for controlling control the transmission of control commands or control information for the data transmission device from the data terminal to the data transmission device in a wireless V.24 data transmission system operating between a data terminal and a data transmission device for data telecommunication.
It is another object of the invention to provide such a way that the recognizability of control commands or control information for the data transmission device is ensured.
These and other objects of the invention will become apparent upon careful review of the detailed description of the preferred embodiments which is to be read in conjunction with a review of the drawing figures.